During hydraulic fracturing activities, just like during drilling activities, the availability of real-time data obtained from a bottom hole (e.g., bottom-hole data) can be very useful. It is hard to install wire communications because an unprotected cable will be cut off by a proppant-containing solution. Using a protected cable seems to be an awkward option too. There are solutions suggesting that an optical cable protected by coil tubing should be used, but these solutions imply new operational complications and increase the costs. The solutions associated with the use of a wired drill string may also fail to handle the erosion problem which occurs due to the use of proppant.
There are a number of hydraulic fracturing activities during which a tubing is inserted into a well (e.g., for protection of the well against the high pressure action). A packer is installed above perforations between the tubing and a string, thus forming a tubing annulus. The tubing annulus is filled with a low-viscosity fluid; the tubing annulus pressure is maintained by using a dedicated pump in order to counteract the tubing pressure. So, the tubing annulus is a low-attenuation acoustic waveguide. Embodiments of telemetry facilities which use this channel have been considered in a number of patents (refer to Patents Nos. RU 2209964 dated Aug. 10, 2003, RU 2310215 dated Oct. 7, 2005) and No. US 2005/0168349 published on Aug. 4, 2005. According to US 2005/0168349, a downhole telemetry system contains at least one pressure pulse generator, at least one pressure transmitter located in an internal tubing, at least one pressure transmitter located in a tubing annulus near the well, and a packer.
The main disadvantage of this system is the need to change the packer sealing procedure, which complicates the process of taking measurements by using the downhole telemetry system.